问题
选择题
空气和二氧化碳按体积比5:1混合，将混合气体与足量的红热焦炭充分反应。设空气中氧气和氮气体积比 为1:4，不计其他成分，且体积都在同温、同压下测定的，则反应后的气体中一氧化碳的体积分数为[ ]
A. 29%
B. 43%
C. 50%
D. 100%
答案
答案：C
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空气和二氧化碳按体积比5:1混合，将混合气体与足量的红热焦炭充分反应。设空气中氧气和氮气体积比 为1:4，不计其他成分，且体积都在同温、同压下测定的，则反应后的气体中一氧化碳的体积分数为[ ]
A. 29%
B. 43%
C. 50%
D. 100%
答案：C
The task(任务)of students is to study．But studying __21__a right way, or we will waste(浪费)time or __22__．The following are some ways of studying .The best time for reading is in the morning ,___23__ in the morning the air is fresh and the mind is clear． __24__studying,we must have patience(耐心).If we have not __25__ a text well，we must read it again.We should not read the next one until we have learnt the first one． When we are __26__，we must put our hearts into the book，or we can get __27__ from the book that we are reading We must always __28__“why” If we can’t understand something well，write it down and ask our teachers，parents or friends Though there are many __29__of studying，the above will be quite enough if we can __30__them in heart and do so.
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